Special thanks to NewSea, an amazing creator for Sims hairs, who finally replied to my emails and gave me permisson to use the beautiful sims hairs converted by HelloSanta.Link to NewSea's homepage in ReadMe.

In Skyrim/Data/Meshes/Actors/Character/FaceGenData/FaceGeom/ElvenSisters.esp/open 00000D62 (for example, if you want change Scarlet's hair) in NifSkope

Just make sure the hairline and hair tint colors are the same:

How to change their VOICE

Open the esp in creation kit, load it (like Skyrim.esm and Update.esm)Single click on actor, and search for their names (that one you want to choose)Double click the name, it will open their windows.Under Traits tab you can select another voice type, just make sure it works fine with followers.